Properties of human brain tissue change across the lifespan. Here we model these changes in the living human brain by combining quantitative magnetic resonance imaging (MRI) measurements of R1 (1/T1) with diffusion MRI and tractography (N=102, ages 7-85). The amount of R1 change during development differs between white-matter fascicles, but in each fascicle the rate of development and decline are mirror-symmetric; the rate of R1 development as the brain approaches maturity predicts the rate of R1 degeneration in aging. Quantitative measurements of macromolecule tissue volume (MTV) confirm that R1 is an accurate index of the growth of new brain tissue. In contrast to R1, diffusion development follows an asymmetric time-course with rapid childhood changes but a slow rate of decline in old age. Together, the time-courses of R1 and diffusion changes demonstrate that multiple biological processes drive changes in white-matter tissue properties over the lifespan.
Bibliographical noteFunding Information:
We thank Jenny Nguyen, Stephanie Phipps, Ryan Martin, Keith Main Le Hua, Netta Levin and Noa Raz for assistance with data collection, and Ariel Rokem, Franco Pestilli, Kevin Weiner and Nathan Withoft for comments on the manuscript. This work was funded by Weston Havens foundation grant to B.A.W., J.D.Y. and A.A.M., NSF BCS1228397 and NIH EY015000 to B.A.W., Human Frontier science programme to A.A.M.
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